1. Field of the Invention
The present invention relates to a coupler used in a transformer section of electric power-lines for digital network communication by means of using a transmitting device, which includes a piezoelectric substrate and four coded interdigital transducers (IDTs).
2. Description of the Prior Art
Electric power-lines are greatly desired to be used for digital network communication. However, the existence of power line transformer, where an electric power-line is separated under high-frequency condition but is not separated electro-magnetically, makes signal transmission difficult. Thus, in order to use the electric power-lines, a coupler, which connects two separated electric power-lines, is necessary. A conventional type of transformer for high-frequency signal transmission employs coils. However, the use of coil causes an electromagnetic coupling. In short, it is difficult for the conventional type of transformer to prevent the influence of noises. In addition, the conventional type of transformer has a problem on transmitting ability because the use of digital pulse-signal is indispensable for digital network communication.
An object of the present invention is to provide a coupler for digital communication on electric power-lines comprising an input connector, an output connector, and a transmitting device.
Another object of the present invention is to provide a coupler for digital communication on electric power-lines capable of transmitting a message-digital signal over a power line transformer without the influence of noises.
Another object of the present invention is to provide a coupler for digital communication on electric power-lines excellent in transmitting ability.
Another object of the present invention is to provide a coupler for digital communication on electric power-lines capable of a low electric power consumption.
Another object of the present invention is to provide a coupler for digital communication on electric power-lines excellent in durability and manufacturing.
A still other object of the present invention is to provide a coupler for digital communication on electric power-lines having a small size which is very light in weight and has a simple structure.
According to one aspect of the present invention there is provided a coupler for digital communication on electric power-lines comprising an input connector connected with first electric power-lines, an output connector connected with second electric power-lines, and a transmitting device, which is connected between the input connector and the output connector, and is located in parallel with a transformer between the first electric power-lines and the second electric power-lines. If a coded message digital-signal is received at the input connector from the first electric power-lines, the coded message digital-signal is tansduced to a coded output digital-signal by the transmitting device. Thus, the coded output digital-signal is delivered from the output connector into the second electric power-lines.
According to another aspect of the present invention there are provided a mixer as the output connector and a transmitting device, which consists of a piezoelectric substrate, a tuning coil, a first intermediary IDT, first-, second-, third-, and fourth coded IDTs, a second intermediary IDT, an electrode group, a synchronizing device, an envelope detecting device, and a pulse generator. The first-, second-, third-, and fourth coded IDTs consist of at least three interdigital electrode pairs, respectively, and have first-, second-, third-, and fourth coded patterns, respectively. The electrode group consists of two sideward IDTs and a central IDT between the sideward IDTs. The synchronizing device is connected between the first intermediary IDT and one of the sideward IDTs. The envelope detecting device is connected with the central IDT. The pulse generator is connected with the envelope detecting device.
If a message digital-signal is received at the input connector from the first electric power-lines, the message digital-signal is applied to the first intermediary IDT via the tuning coil. In this time, if the message digital-signal is composed of a row of pulse-groups, of which each is composed of a coded row of pulses, a first surface acoustic wave (SAW) composed of a coded row of burst-waves is excited on the piezoelectric substrate. When the first SAW corresponds to the first coded pattern, a first decoded pulse is detected at the first coded IDT. In the same way, when the first SAW corresponds to the second coded pattern, a second decoded pulse is detected at he second coded IDT. The first- and second decoded pulses are applied to the third coded IDT and the fourth coded IDT, respectively. In this time, second- and third SAWs corresponding to the third- and fourth coded patterns, respectively, are excited on the piezoelectric substrate. And then, a coded burst-signal corresponding to the second- and third SAWs, respectively, is detected at the second intermediary IDT. When the coded burst-signal arrives at the two sideward IDTs simultaneously, fourth- and fifth SAWs are excited on the piezoelectric substrate, respectively. The fourth- and fifth SAWs arrive at the central IDT simultaneously. And the coded digital-signal corresponding to the third- and fourth coded patterns, respectively, is obtained at the envelope detecting device. Thus, an output digital-signal, which is based on the coded digital-signal and is equivalent to the message digital-signal, is generated at the pulse generator. And then, the output digital-signal is delivered via the mixer into the second electric power-lines.
According to another aspect of the present invention there is provided a coupler for digital communication on electric power-lines, wherein a propagation direction of the first SAW is orthogonal to that of the second- and third SAWs.
According to another aspect of the present invention there is provided a coupler for digital communication on electric power-lines, wherein a propagation direction of the second- and third SAWs is orthogonal to that of the fourth- and fifth SAWs.
According to another aspect of the present invention there are provided first- and second coded IDTs having a different number of interdigital electrode pairs from third- and fourth coded IDTs, respectively.
According to another aspect of the present invention there are provided third- and fourth coded patterns in reverse to first- and second coded patterns, respectively.
According to another aspect of the present invention there are provided first-, second-, third-, and fourth coded patterns changed in accordance with a designated time region, respectively.
According to other aspect of the present invention there is provided a piezoelectric substrate made of a piezoelectric ceramic, the polarization axis thereof being parallel to the thickness direction thereof.
According to a further aspect of the present invention there is provided a bipolar-pulse generator in place of the pulse generator.